The present invention relates to a substrate holder which is mounted on a substrate transfer apparatus, such as a robot, for holding and transferring a thin substrate such as a semiconductor wafer. The present invention also relates to a substrate transfer apparatus using the above-mentioned substrate holder.
FIGS. 1(a)-1(b) show an arrangement of a conventional substrate holder of the above-mentioned type. FIG. 1a is a plan view and FIG. 1(b) is a side view. As shown in FIG. 1(a), the conventional substrate holder comprises a substrate support member 100 including a base portion 101 and finger portions 102 extending from the base portion 101 in a bifurcated form. Each finger portion 102 includes a vacuum opening 103 at a forward end portion thereof Further, a vacuum passage 104 extends through the finger portion 102 so as to communicate with the opening 103. The respective vacuum passages 104 of the finger portions 102 join at the base portion 101 and communicate with an opening 105 which in turn communicates with a vacuum system (not shown).
In the above-mentioned substrate holder, a substrate is held by means of suction. Illustratively stated, a thin substrate (not shown), such as a semiconductor wafer, is provided in the holder so that a central portion of a backside of the substrate abuts against the vacuum openings 103 of the finger portions 102. A vacuum pressure is applied through the openings 103, thus holding the substrate on the finger portions 102. In FIG. 1(a), reference numeral 106 denotes a bolt opening. The substrate holder is fixed to a forward end of a robot (not shown) by passing bolts through the openings 106.
As mentioned above, in the conventional substrate holder, the central portion of the backside of the substrate is suctioned onto the finger portions 102. Therefore, a problem arises, such that when breakage of a vacuum source occurs during transfer of a substrate, a vacuum pressure cannot be applied to the substrate, with the result that the substrate is likely to fall from the substrate holder and break. Further, particles floating in air are collected at the portion of the substrate to which the vacuum pressure is applied, leading to contamination of the substrate. These particles adversely affect the manufacture of chips for semiconductors and therefore the amount thereof should be minimized.
Further, when the speed of transfer (the speed of movement of the substrate holder) is increased so as to achieve a reduction in tact time, a force which horizontally moves the substrate becomes large, so that the substrate mounted on the holder is displaced. Therefore, the substrate cannot be delivered accurately to a target position, so that there is a risk of damage to the substrate.
In recent years, in semiconductor manufacturing apparatuses, it has been strongly desired to prevent contamination of semiconductor substrates. Conventionally, preventing only contamination of a patterned surface was satisfactory, but with a recent tendency to reduce wiring line widths of devices, contamination of the backside of a substrate has also become problematic. In a conventional substrate holder in which a suction is utilized, contaminants are collected at a portion of the substrate to which vacuum is applied from the holder, leading to a high risk of contamination.
As a measure to obviate the above-mentioned problem of contamination, it is considered to employ a recessed type substrate holder comprising a substrate support member having a recessed area for placing a semiconductor substrate therein. However, when a semiconductor substrate is removed from a cassette case, the semiconductor substrate is not always positioned at a regular position in the cassette case, that is, a position where the center of the substrate and the center of the cassette case coincide with each other. That is, the substrate can be displaced from the regular position in the cassette case. In this case, when use is made of a substrate holder having a portion formed in a certain configuration for receiving a substrate, such as the above-mentioned conventional substrate holder, defective transfer due to displacement of the substrate is likely to occur.
In view of the above, the present invention has been made. It is an object of the present invention to provide a substrate holder which is free from the above-mentioned problems. The substrate holder of the present invention is capable of suppressing contamination of a substrate due to particles, eliminating the risk of breakage of a substrate falling from the holder, receiving a substrate accurately even when it is displaced from a regular position and delivering the substrate accurately to a regular position. It is another object of the present invention to provide a substrate transfer apparatus using the above-mentioned substrate holder.
In accordance with the present invention, there is provided a substrate holder for holding and transferring a thin substrate, comprising a substrate support member having a recessed area for receiving a thin substrate therein and substrate mount portions formed in the recessed area in the vicinity of a circumferential edge thereof. The substrate mount portions are adapted to be engaged with an outer circumferential portion of a substrate placed in the recessed area. The substrate holder also includes a substrate detector for detecting presence or absence of the substrate in the recessed area.
In the substrate holder, there is little risk of displacement of the substrate and breakage of the substrate due to falling from the holder. Further, only the outer circumferential portion of the backside of the substrate abuts against the substrate mount portion, so that it is possible to suppress contamination of the substrate due to deposition of particles at a portion of the backside of the substrate which does not abut against the substrate mount portion.
The substrate detector may comprise at least one detection means selected from a first detection means and a second detection means and a second detection means. The first detection means includes a substrate detecting portion which is formed in the recessed area in the vicinity of a circumferential edge thereof. The substrate detecting portion has surface with which the outer circumferential portion of the backside of the substrate received in the recessed area is engaged, and a fluid passage is provided in the substrate holder and has an opening formed in the stated surface of the substrate detecting portion. The first detection means is adapted to detect presence or absence of the substrate by detecting a pressure in the stated opening. The second detection means is a non-contact type which detects presence or absence of the substrate in the recessed area without making contact with the substrate.
In the substrate holder, a fluid such as clean air or N2 gas is flowed at a low rate through the opening of the fluid passage to the outside. The presence or absence of the substrate is detected by detecting whether or not a change in pressure occurs due to closing of the opening by the substrate. Differing from the conventional technique in which the presence or absence of the substrate is detected according to a change in vacuum pressure, in the substrate holder, there is no possibility of contamination of a substrate due to collection of particles floating in air. Further, when the detector is a non-contact type, such as a photoelectric sensor, the detector detects the presence or absence of the substrate in the recessed area without making contact with the substrate. This enables rapid detection of displacement of the substrate during transfer and is advantageous in preventing breakage of the substrate due to it falling from the holder. Further, when the opening of the fluid passage is connected to a vacuum source during transfer of the substrate, lifting of the substrate (hence displacement of the substrate) can be prevented. In this case, a high vacuum pressure is not required and only the outer circumferential portion of the backside of the substrate is suctioned, so that contamination of the substrate due to particles can be suppressed.
According to another aspect of the present invention, provided is a substrate holder for holding and transferring a thin substrate. This substrate holder comprises a substrate support member having a recessed area for placing a thin substrate therein, and substrate amount portions formed in the recessed area in the vicinity of a circumferential edge thereof The substrate mount portions are adapted to be engaged with an outer circumferential portion of a backside of the substrate. The substrate support member has a first portion adapted to be connected to a substrate transfer apparatus and a second portion in which the recessed area is formed. The second portion includes a proximal section close to the first portion with a large width and a distal section apart from the first portion with a small width.
The holder is advantageous in receiving a substrate from a cassette case of which an inner width is limited and delivering the substrate to such a cassette case, and enables the substrate to be stably held on the holder.
According to another aspect of the present invention, a substrate holder comprises a substrate support member having a recessed area for placing the substrate therein. The substrate support member has a first portion adapted to be connected to a substrate transfer apparatus and a second portion in which the recessed area is formed. The second portion includes a proximal portion close to the first portion and a distal section apart from the first portion. The proximal portion is thicker than the distal portion. This arrangement enables lightening of the substrate support member.
According to a further aspect of the present invention, a substrate holder comprises a substrate support member having a recessed area for receiving the substrate therein and an aligning mechanism adapted to perform a function such that when the substrate support member is moved to a position where a substrate should be placed in order to receive the substrate, and when the substrate is actually displaced from the position, the aligning mechanism moves the substrate to the position thereby enabling the substrate support member to receive the substrate appropriately.
Specifically, the aligning mechanism comprises an aligning member provided outside and in the vicinity of the recessed area of the substrate support member in such a manner that when the substrate support member is moved towards an area below the substrate so as to receive the substrate, the aligning member engages and moves the substrate to the above-stated position.
Further, the present invention provides a substrate transfer apparatus that comprises a substrate holder such as stated above.
Furthermore, the present invention provides a substrate transfer apparatus suitable for use in a substrate treatment apparatus including a substrate loading/unloading station and a substrate treatment station where the substrate is treated. The substrate transfer apparatus comprises a first substrate holder for holding a pre-treatment substrate by means of suction and transferring the pre-treatment substrate to the substrate treatment station, a second substrate holder for holding a post-treatment substrate which has been treated in the substrate treatment station to return the post-treatment substrate to return the post-treatment substrate to the loading/unloading station. The second substrate holder comprises a substrate support member having a recessed area for placing the post-treatment substrate therein and substrate mount portions formed in the recessed area in the vicinity of a circumferential edge thereof The substrate mount portions are adapted to be engaged with an outer circumferential portion of a backside of the post-treatment substrate placed in the recessed area. The second substrate holder also includes a substrate detector for detecting presence or absence of the post-treatment substrate in the recessed area.
The present invention further provides a polishing apparatus comprising a loading/unloading station, a polishing station for polishing a substrate, a cleaning and-drying station for cleaning and drying the substrate polished in the polishing station, and a substrate transfer apparatus for transferring the substrate between the stated stations. The substrate transfer apparatus comprises a first substrate holder for holding a substrate, which has not been subjected to polishing in the polishing station, by means of suction and transferring the substrate to the polishing station, and a second substrate holder for holding a substrate, which has been polished in the polishing station, and returning the substrate to the loading/unloading station. The second substrate holder comprises a substrate support member having a recessed area for placing the substrate therein and substrate mount portions formed in the recessed area in the vicinity of a circumferential edge thereof The substrate mount portions are adapted to the engaged with an outer circumferential portion of a backside of the substrate placed in the recessed area. The second substrate holder also includes a substrate detector for detecting presence or absence of the substrate in the recessed area.